JPS62103073A - Method of purifying ethylene oxide - Google Patents

Abstract

PURPOSE:To purify EO in high energy efficiency, by using steam produced by heat energy of a stripped material of an EO stripping column and of a solution at the bottom of the stripping column recovered by a heat pump as a heating source for an EO fractionating column. CONSTITUTION:A solution at the bottom of an ethylene oxide(EO) absorbing column 2 is subjected to heat exchange by a heat exchanger 6 with a solution at the bottom of an EO stripping column 11, an inert gas is separated by a separator 8 and fed to the stripping column 11. An EO-containing stripped material from the stripped column 11 is fed to the heater 60 of an EO fractionating column 50, used as a heating source for the fractionating column 50, sent to a condenser 64, an uncondensed gas is fed through a dehydrating column 29 and a separating column 40 to the fractionating column 50 and a purified EO is recovered 57. The solution at the bottom of the stripping column 11 is subjected to heat exchange with a solution at the bottom of an absorbing solution by the heat exchanger 6, sent to a refrigerant evaporator 16 of a heat pump, further cooled 17 and refluxed as an absorbing solution to the absorbing column. The refrigerant evaporated by the evaporator 16 is compressed 70, sent to a refrigerant condenser 73, water circulating in it is heated to produce steam, which is fed to a heater 58 of the fractionating column 50 and used as a heating source.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for purifying ethylene oxide. A reaction product gas containing ethylene oxide produced by contact gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower, brought into countercurrent contact with the absorption liquid, and is removed from the top of the ethylene oxide absorption tower. The gas is circulated to the ethylene oxidation reaction step, the ethylene oxide absorption tower bottom liquid containing ethylene oxide is supplied to an ethylene oxide stripping tower, ethylene oxide is diffused from the top of the ethylene oxide stripping tower, and the distillate containing ethylene oxide and water is condensed. In the process of separating water in a dehydration tower, separating heavy fractions in a heavy fraction separation tower, and then rectifying ethylene oxide in an ethylene oxide rectification tower, the heat of condensation of the emissions from the ethylene oxide stripping tower is used. A method for purifying ethylene oxide that reduces the heating energy of an ethylene oxide rectification column, in which heat is recovered from the ethylene oxide stripping column bottom liquid using a heat pump, and the low-pressure steam generated by the heat recovery is used as a heat source for the ethylene oxide rectification column. It is related to.

(Prior Art) Ethylene oxide is generally purified as follows. The reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene and molecular oxygen-containing gas over a silver catalyst is led to an ethylene oxide absorption tower, brought into countercurrent contact with an absorption liquid mainly composed of water, and recovered as an ethylene oxide aqueous solution. Then, it is sent to an ethylene oxide stripping tower and the bottom of the ethylene oxide stripping tower is heated with heated steam to diffuse ethylene oxide from the aqueous solution.The aqueous solution that does not substantially contain ethylene oxide from the bottom of the ethylene oxide stripping tower is recycled as an absorption liquid and is then sent to the ethylene oxide stripping tower. Ethylene oxide, water, carbon dioxide released from the top,
In addition to inert gases (nitrogen, argon, methane, ethane), emissions containing low-boiling point impurities such as formaldehyde and high-boiling point impurities such as acetaldehyde and acetic acid are removed during the dehydration process.
Ethylene oxide can be produced by purification through a heavy fraction separation step and a heavy fraction separation step.

(Problems to be Solved by the Invention) However, such a method for purifying ethylene oxide requires recovery of the heat of condensation of the vapor at the top of the ethylene oxide dispersion column and recovery of thermal energy possessed by the liquid extracted from the bottom of the ethylene oxide dispersion column. There was a problem that the amount of heat was not sufficient and a large amount of heat was discarded outside the system. In the conventional method, the ethylene oxide stripping tower bottom liquid at 100 to 130°C is heat exchanged with the ethylene oxide absorption tower bottom liquid, and after recovering the heat amount, it is cooled and used as the absorption liquid of the ethylene oxide absorption tower. Furthermore, the method for purifying ethylene oxide has a problem in that the amount of heated steam in the ethylene oxide rectification column is consumed by Kamaishi. The present invention was developed as a result of research into energy saving in these ethylene oxide rectification processes.
The present invention was completed by focusing on the effective use of the energy of the ethylene oxide stripping tower bottom liquid and the energy of the ethylene oxide stripping tower top steam.

(Means for solving the problem) A reaction product gas containing ethylene oxide produced by catalytic gas-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower and exchanged with the absorption liquid. A part of the gas from the top of the ethylene oxide absorption tower is circulated to the ethylene oxidation reaction process, and the ethylene oxide absorption tower bottom liquid containing ethylene oxide is supplied to the ethylene oxide stripping tower, where ethylene oxide is diffused from the top of the ethylene oxide stripping tower. and a step of condensing the distillate containing water, separating water in a dehydration tower, leading to a heavy fraction separation tower to separate the heavy fraction, and then leading to an ethylene oxide rectification tower to rectify ethylene oxide, The emitted material emitted from the ethylene oxide stripping tower is used as a heating source for the ethylene oxide rectification tower, and the liquid extracted from the bottom of the ethylene oxide stripping tower is guided to the ethylene oxide absorption tower and recycled as an absorption liquid.The remainder is used as the ethylene contained in the absorption liquid. In the process of sending the by-product ethylene glycol to the concentration tower to concentrate glycol, the liquid extracted from the bottom of the ethylene oxide diffusion tower is heat exchanged with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then a heat pump is used to extract the heat of the absorption liquid. Energy is recovered to generate water vapor, which is used as a heating source for the ethylene oxide rectification tower, and the absorption liquid cooled by the heat pump is further cooled by the cooling source, and then used as the absorption liquid for the ethylene oxide absorption tower. The present invention relates to a method for purifying ethylene oxide.

In the present invention, the temperature of the absorption liquid supplied to the ethylene oxide absorption tower is 5 to 40°C, preferably 10 to 35°C, and the composition of the absorption liquid has a pH of 5 to 12, preferably 6 to 1.
1. The ethylene glycol concentration is controlled within the range of 1 to 40% by weight, preferably 5 to 30% by weight, the antifoaming agent concentration is O; In order to keep the ethylene glycol concentration in the absorption liquid constant, a part of the absorption liquid that circulates between the ethylene oxide absorption tower and the ethylene oxide stripping tower is extracted from the bottom of the ethylene oxide stripping tower and sent to the by-product ethylene glycol concentration tower, where it is freshly recycled if necessary. water is introduced and controlled.

It is preferable to adjust the pH by adding a compound that dissolves in the absorption liquid, such as a hydroxide or carbonate of an alkali metal such as potassium or sodium. Specifically, the additive is potassium hydroxide or Sodium hydroxide is preferred.

Any antifoaming agent can be used as long as it is inert to ethylene oxide, by-product ethylene glycol, etc. and has an antifoaming effect on the absorption liquid.A typical example is a water-soluble silicone emulsion. It is effective because it has excellent dispersibility in liquids, dilution stability, and thermal stability.

The operating conditions for the ethylene oxide absorption tower are such that the ethylene oxide concentration in the reaction product gas is 0.5 to 5% by volume, preferably 1.0 to 4% by volume, and the operating pressure of the ethylene oxide absorption tower is preferably 2 to 40 KO/ciG1. is 10-30
Kq/ciG.

The operating conditions for the ethylene oxide stripping tower are an ethylene oxide stripping tower top pressure of 0.1 to 2. Oka/a+fG.

Preferably 0.3-0.6 kg/dG, ethylene oxide stripping tower top temperature 85-120°C, ethylene oxide stripping tower bottom temperature 100-130°C, ethylene oxide stripping tower bottom ethylene oxide concentration 10 ppm or less, preferably 0
．． It is 5 ppm or less.

In the present invention, the temperature of the supplied steam supplied to the ethylene oxide dehydration tower is 5 to 60°C, preferably 10 to 50°C, and the ethylene oxide concentration of the supplied steam is in the range of 80 to 98% by weight.

The operating conditions for the ethylene oxide dehydration tower are dehydration tower top pressure O
~2kQ/ciG, preferably 0.3-0
6 kq/iG, a dehydration tower top temperature of 10 to 40°C, and a dehydration tower bottom temperature of 100 to 130°C. The concentration of ethylene oxide at the bottom of the dehydration tower is 1100 pl) or less, preferably 10 pl.
The range is below pm.

In the present invention, the temperature of the feed liquid supplied to the ethylene oxide light fraction separation column is 0 to 50°C, preferably 5 to 30°C.
The composition of the feed liquid is mostly ethylene oxide,
Contains a small amount of aldehydes such as formaldehyde and water.

The operating conditions of the light fraction separation tower for ethylene oxide are a light fraction separation tower top pressure of 1 to 10 kq/cIdG, preferably 3 to 7
It is in the range of ka/dG.

The light fraction separation tower top temperature is in the range of 30 to 90°C, and the light fraction separation tower bottom temperature is in the range of 30 to 90°C.

Light fraction separation column bottom ethylene oxide concentration is 99.5% by weight
The content is preferably 99.95% by weight or more.

In the present invention, the ethylene oxide rectification column includes a tray column type and a packed column type. There are various types of trays in the tray column type distillation column, including bubble cap trays, uni-flux trays, turbo grid trays, lip trays, flexi trays, sieve trays, and ballast trays. Packing materials for packed column type rectification columns include Raschig rings, ball rings, saddle rings, spiral rings, McMahon backings, Interlocks metal backings, and pressure loss of 2' to 3 mmt-H per theoretical plate number. For example, a wire mesh laminate having a filling, a woven or knitted structure, and the like.

In the present invention, the temperature of the feed liquid supplied to the ethylene oxide rectification column is 30 to 90°C, preferably 50 to 70°C, and the composition of the feed liquid is such that the ethylene oxide concentration is 99.5°C.
The weight is controlled to be at least 99.95% by weight, preferably at least 99.95% by weight.

The operating conditions for the ethylene oxide rectification column are a rectification column top pressure of 1.0 to 8.0 kcx/iG, preferably 2.0 to 5.0 kcx/iG.
0 kQ/dG, rectification tower top temperature 40 to 65°C, rectification tower top pressure 45 to 70°C, rectification tower bottom ethylene oxide degree a is 30
The range is from 40 to 80% by weight, preferably from 40 to 80% by weight.

In the present invention, the rectification column bottom liquid is a heavy fraction consisting of high boiling point impurities such as acetaldehyde, water and acetic acid.

A feature of the present invention is that a reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower and brought into countercurrent contact with an absorption liquid, A portion of the gas from the top of the ethylene oxide absorption tower is recycled to the ethylene oxidation reaction process.
The ethylene oxide absorption tower bottom liquid containing ethylene oxide is supplied to the ethylene oxide stripping tower, and the ethylene oxide is diffused from the top of the ethylene oxide stripping tower, and the liquid extracted from the bottom of the ethylene oxide stripping tower is heat exchanged with the ethylene oxide absorption tower bottom liquid in a heat exchanger. After being cooled in a cooler, it is led to an ethylene oxide absorption tower and recycled as an absorption liquid, and the remainder is dissipated from an ethylene oxide stripping tower in the process of sending it to a by-product ethylene glycol concentration tower to concentrate the ethylene glycol contained in the liquid. The aim is to recover the thermal energy possessed by the steam produced by the steam, and to make effective use of the recovered thermal energy. As a means of achieving this, the vapor emitted from the ethylene oxide stripping tower is sent to the heater of the ethylene oxide rectification tower, where heat is exchanged and the emitted material is liquefied.
A method is adopted in which the condensed liquid is far-flowed to an ethylene oxide stripping tower, and the uncondensed gas is supplied to a dehydration tower. Further, the liquid extracted from the bottom of the ethylene oxide stripping tower exchanges heat with the ethylene oxide absorption tower bottom liquid in a heat exchanger, and after recovering the thermal energy of the absorption liquid using a heat pump, it is sent to a cooler.

The refrigerant used as the working fluid of the heat pump used in the present invention is used in circulation by repeating evaporation and condensation in the heat pump process, so in addition to its thermodynamic properties, the refrigerant must be thermally and chemically stable. In terms of safety and handling, it is required that the material be odorless, non-toxic, and non-explosive. Refrigerants that can be used in the present invention include R-11, R-
Examples include fluorinated hydrocarbons such as 12, R-22, R-113 and R-114, and hydrocarbons such as propane and pentane, but considering the heat pump operating temperature conditions, R
-12 and R-114 are most suitable.

The operating conditions for the heat pump of the present invention are such that the ethylene oxide stripping column bottom liquid, which comes out from the bottom of the ethylene oxide stripping column and which does not substantially contain ethylene oxide and whose heat is recovered by the ethylene oxide absorption column bottom liquid and the heat exchanger, is 50 to 60°C.
The refrigerant enters the refrigerant evaporator at a temperature of be done.

The refrigerant evaporated in the refrigerant evaporator using the ethylene oxide stripping column bottom liquid is compressed by a centrifugal, screw, or reciprocating compressor to a pressure at which the saturation temperature of the refrigerant is 80 to 100°C. The pressurized refrigerant is given heat to the outside by the following two methods, condensed, and sent to the refrigerant evaporator by a pump for circulation.

0) The refrigerant vapor is directly sent to another rectification column, such as an ethylene oxide rectification column (bottom temperature: 50 to 70°C) and a glue boiler, where it is condensed, and the heat of condensation is given to the precision column bottom liquid.

(2) Sending refrigerant vapor to the refrigerant condenser, giving latent heat of condensation to the fluid in the refrigerant condenser, such as water, and condensing the refrigerant.

A fluid, such as water, which has been given heat by the refrigerant, is heated to a temperature 5 to 10 degrees Celsius lower than the temperature of the refrigerant, and low-pressure steam is generated by flashing, which can be used.

In the present invention, the high-temperature liquid from the bottom of the ethylene oxide stripping tower exchanges heat with the low-temperature liquid from the bottom of the ethylene oxide absorption tower, recovers heat, and is supplied to the ethylene oxide absorption tower.

On the other hand, the ethylene oxide absorption tower bottom liquid undergoes heat exchange with the ^-temperature liquid from the bottom of the ethylene oxide stripping tower, and after separating the light component gas in a gas-liquid separation tank, it is supplied to the top of the ethylene oxide stripping tower where ethylene oxide is diffused. be done. In the present invention, what is emitted from the ethylene oxide stripping tower is mostly water and ethylene oxide, with a small amount of carbon dioxide, trace amounts of oxygen, ethylene, and inert gases (nitrogen,
It is an emissive product consisting of low-boiling point impurities such as argon, methane, ethane) and formaldehyde, and high-boiling point impurities such as acetaldehyde and acetic acid.

In order to describe the present invention in more detail, the present invention will be explained based on FIG.

In Figure 1, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through a conduit (1) to an ethylene oxide absorption tower in the form of a packed column or tray column. (2), and the absorption liquid is introduced into the upper part of the ethylene oxide absorption tower (2) through the conduit (3), brought into countercurrent contact with the reaction product gas, and absorbs ethylene oxide in the reaction product gas into the absorption liquid. let At this point, 99% by weight or more of ethylene oxide in the reaction product gas is recovered. Ethylene, oxygen, carbon dioxide, and inert gases (nitrogen, argon, methane,
Gases such as ethane), aldehydes, and acidic substances are contained in the conduit (4).
is recycled to the carbon dioxide absorption step and/or oxidation reaction step. In this absorption process, in addition to ethylene oxide, ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane, etc.), low-boiling point impurities such as formaldehyde generated in the ethylene oxidation reaction process, and high-boiling point impurities such as acetaldehyde and acetic acid are used. A substantial amount of impurities are also absorbed at the same time.

The bottom liquid of the ethylene oxide absorption tower (2) is sent through the conduit (5) to the heat exchanger (6), where it exchanges heat with the ethylene oxide dispersion column bottom liquid to raise the temperature to 70 to 110°C, and then is separated into gas and liquid through the conduit (7). The light gas, which is an inert gas containing some ethylene oxide and water, is sent to the tank (8), and the light gas is sent to the conduit (9).
separated by The remaining absorption liquid after flushing the light gas is passed through the conduit (10) at a pressure of 0.1 to 2 Kq/c.
dG, ethylene oxide stripping tower with a temperature of 85 to 120°C (
The ethylene oxide stripping tower (11) is supplied to the upper part of the ethylene oxide stripping tower (11).
) to the heater (12) through a conduit (13) to supply a heating medium such as steam or Dowsum (a heating medium product of Dow Co., Ltd. in the United States), or directly to the ethylene oxide stripping tower (11).
By using a heating method that introduces water vapor into the bottom of the tank, more than 6% of 99% of ethylene oxide is released. A portion of the ethylene oxide stripping column bottom liquid, which is substantially free of ethylene oxide and has a temperature of 100 to 130° C., is introduced from the bottom of the ethylene oxide stripping column (11) through the conduit (14) and the conduit (15) into the heat exchanger (6). Ethylene oxide absorption tower (
Heat is exchanged with the bottom liquid of 2).

The absorption liquid leaving the heat exchanger (6) passes through a refrigerant evaporator (16) and then is cooled by a cooler (17), and fresh water is then passed through a conduit (21) to adjust the ethylene glycol concentration in the absorption liquid. ), and if necessary, add an aqueous potassium hydroxide solution to adjust the pH in the absorption liquid, and introduce the antifoaming agent into the ethylene oxide absorption tower (2) to adjust the antifoaming agent concentration in the absorption liquid. I can do it.

On the other hand, during the oxidation process in which ethylene is oxidized with molecular oxygen and the ethylene oxide diffusion process, low-boiling impurities such as by-product ethylene glycol and formaldehyde, acetaldehyde, acetic acid, etc., are produced by the hydrolysis reaction of ethylene oxide and water in the absorption liquid. In order to prevent an increase in high-boiling point impurities, a conduit (1
The remaining absorption liquid extracted through 4) is sent to the by-product ethylene glycol concentration column through the conduit (22).

The refrigerant evaporated through heat exchange with the bottom liquid of the ethylene oxide stripping tower in the refrigerant evaporator (16) is sent to the compressor (70) through the conduit (71) and compressed, and is then condensed through the conduit (72). J (73), which gives heat to the external fluid and condenses it. The condensed refrigerant is sent again to the refrigerant evaporator (16) through the conduit (74).

Water vapor can be recovered through the conduit (59) by circulating water supplied through the conduit (78) to the refrigerant condenser (73), the conduit (76), the conduit (77), and the tank (75).

This recovered steam can be effectively used as a heating source in the ethylene oxide manufacturing process. In particular, this steam can be used as a heating source for the ethylene oxide rectification column (5o).

On the other hand, the vapor containing ethylene oxide released from the top of the ethylene oxide stripping tower (11) is transferred to the conduit (23).
) to the heater (60) of the ethylene oxide rectification column (50) as a heating source, and then the condensed liquid and uncondensed vapor pass through the conduit (61) to the conduit (62) and the conduit (63).
), the condensed liquid is refluxed to the top of the ethylene oxide stripping tower (11) through the conduit (65), and the uncondensed vapor is sent to the dehydration tower (29) through the conduit (66). Supplied.

A heating method in which the heater (30) of the dehydration tower (29) heats the water vapor or a heating medium such as Dow Sam (product of Dow Company) through the conduit (31), or directly introduces steam into the lower part of the dehydration tower (29). Heated with dehydration tower (29)
Ethylene oxide-free water is withdrawn from the bottom of the column through a conduit (32).

Steam containing ethylene oxide is passed from the top of the dehydration tower (29) through the conduit (33) to the conduit (35) and the conduit (
A part of the condensate is sent to the condenser 5 (34) through which cooling water passes through the conduit (36), and a part of the condensate is refluxed to the top of the dehydration tower (29) through the conduit (37). 39) to a re-ethylene oxide absorption tower (not shown).

The other part of the condensate passes through the conduit (38) to the heavy fraction separation column (4).
0).

Ethylene oxide vapor containing heavy gas from the top of the heavy fraction separation column (40) passes through the conduit (43) to the condenser (4
4), the condensate is refluxed to the top of the heavy fraction separation column (40) through the conduit (47), and uncondensed vapor is sent to the conduit (48).
) is fed to a re-ethylene oxide absorption tower (not shown) for recovery of ethylene oxide.

The bottom liquid of the heavy fraction separation column (40) is supplied to the rectification column (50) through a conduit (49).

The emitted material from the top of the ethylene oxide stripping tower (11) is supplied to the heater (60) of the rectifying tower (50), and the rectifying tower (
Heat is recovered from the ethylene oxide absorption liquid using a heat pump in the heater (58) of the ethylene oxide absorption liquid, and the water vapor generated from the tank (75) is heated through the conduit (59). Bottom temperature of 35-80℃, ethylene oxide precision bottom pressure of 1.
Rectification is carried out at 1 to 8.1 ka/ajG, and the top temperature from the top of the ethylene oxide rectification column is 35 to 75°C, and the top pressure is 1.
~8kQ/cdG of ethylene oxide vapor is introduced into the conduit (51
) to an ethylene oxide condenser (52);
Ethylene oxide was liquefied, and a portion was supplied as a reflux liquid to the top of the ethylene oxide rectification column (50) through a conduit (56), and the other portion was extracted as an ethylene oxide product through a conduit (57). The bottom liquid of the ethylene oxide rectification column (50) is passed through a conduit (67) as necessary to separate heavy fractions of high-boiling point impurities such as acetaldehyde and acetic acid.
extracted through.

In order to describe the present invention in more detail, a conventionally known method for purifying ethylene oxide will be explained based on FIG.

In Figure 2, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through a conduit (1) to an ethylene oxide absorption tower in the form of a packed column or tray column. (2), the absorption liquid is introduced into the upper part of the ethylene oxide absorption tower (2) through the conduit (3), and brought into countercurrent contact with the reaction product gas, so that 99% or more of ethylene oxide in the reaction product gas is removed. The gases such as ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane), aldehydes, and acidic substances that were not absorbed from the top of the ethylene oxide absorption tower (2) are stored in a dedicated pipe (4). is recycled to the carbon dioxide absorption step and/or oxidation reaction step. In this absorption process, in addition to ethylene oxide, ethylene,
A substantial amount of oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane, etc.) as well as low-boiling point impurities such as formaldehyde produced in the ethylene oxidation reaction process and high-boiling point impurities such as acetaldehyde and acetic acid are also absorbed at the same time. The bottom liquid of the ethylene oxide absorption tower (2) is transferred to the conduit (
5) is sent to the heat exchanger (6) to exchange heat with the bottom liquid for ethylene oxide dispersion to raise the temperature to 70 to 110°C. The light component of the active gas is passed through the conduit (9)
separated by The remaining absorption liquid after flushing the light gas is passed through the conduit (10) to a tower top pressure of 0.1 to 2 kg.
/cdGS'/M is supplied to the upper part of the ethylene oxide stripping tower (11) at a temperature of 85 to 120°C, and heated by the heater (12) of the ethylene oxide stripping tower (11). By heating with a medium through the conduit (13) or by a heating method of directly introducing steam into the bottom of the ethylene oxide stripping tower (11), 99% by weight of the ethylene oxide contained in the absorption liquid is heated.
At a temperature of 10°C at which ethylene oxide is substantially free from the bottom of the ethylene oxide stripping tower (11),
A portion of the ethylene oxide stripping bottom liquid at 0 to 130°C passes through the conduit (14) and conduit (15) to the heat exchanger (6).
to exchange heat with the bottom liquid of the ethylene oxide absorption tower (2),
cooling by a cooler (17) through which cooling water passes through the conduit (16) and further into the conduit (18) and the conduit (19);
Then, fresh water is introduced through the conduit (21) to adjust the ethylene glycol concentration in the absorption liquid, and if necessary, an aqueous potassium hydroxide solution is added to adjust the I)H in the absorption liquid. In order to adjust the antifoam agent In, an antifoam agent can be introduced into the ethylene oxide absorption column (2) in each case. During the oxidation process in which ethylene is oxidized with molecular oxygen and the ethylene oxide diffusion process, low boiling point impurities such as by-product ethylene glycol and formaldehyde, which are produced by the hydrolysis reaction of ethylene oxide and water in the absorption liquid, and high boiling point impurities such as acetaldehyde and acetic acid. In order to prevent an increase in impurities, the bottom liquid of the ethylene oxide stripping column (11) is extracted from the bottom of the ethylene oxide stripping column (11) through conduits (14) and (22) and sent to a by-product ethylene glycol concentration step.

On the other hand, the vapor containing ethylene oxide released from the top of the ethylene oxide stripping tower (11) is transferred to the conduit (23).
) to the condenser (24) through which cooling water passes through the conduit (25) and conduit (26), the condensate is refluxed to the top of the ethylene oxide stripping tower (11) through the conduit (27), and uncondensed vapor is Dehydration tower (29) through conduit (28)
supplied to

A heating method in which the heater (30) of the dehydration tower (29) heats the water vapor or a heating medium such as Dow Sam (product of Dow Company) through the conduit (31), or directly introduces steam into the lower part of the dehydration tower (29). Heated with dehydration tower (29)
Ethylene oxide-free water is withdrawn from the bottom of the column through a conduit (32).

Steam containing ethylene oxide is passed from the top of the dehydration tower (29) through the conduit (33) to the conduit (35) and the conduit (
A portion of the condensed liquid is returned to the top of the dehydration tower (29) through the conduit (37), and uncondensed vapor in the condenser (34) is sent to the condenser (34) through which cooling water passes through the conduit (36). 39) to a re-ethylene oxide absorption tower (not shown).

The other part of the condensate from the condenser (34) is fed through a conduit (38) to a light fraction separation column (40).

The heater (41) of the light fraction separation column (40) is used to heat the conduit (42) with a heating medium such as steam or Dow Sam (product of Dow Company).
), the light fraction separation column (
Ethylene oxide vapor containing light components is sent from the top of the column (40) to the condenser (44) through a conduit (43), and the condensate is sent to the top of the light fraction separation column (40) through a conduit (47). i! The uncondensed vapors are fed through conduit (48) to a re-ethylene oxide absorber (not shown) for recovery of ethylene oxide.

It is supplied from the bottom of the light fraction separation column (40) to the ethylene oxide rectification column (50) through a conduit (49).

Steam at a pressure of 0.5 to 1.0 ka/aiG is supplied from the conduit (52) to the heater (51) of the ethylene oxide rectification column (50), and the bottom temperature of the ethylene oxide rectification column (50) is 62°C. Fractionation column bottom pressure 3.7kQ/
Rectification is performed using CdG, and ethylene oxide vapor at a top temperature of 54°C and a top pressure of 3.5 ka/aiG is passed from the top of the ethylene oxide rectification column to a condenser (52) through a conduit (51).
) The ethylene oxide vapor is liquefied, and the liquefied part is passed through the conduit (56) to the ethylene oxide rectification column (50
) is introduced as a reflux liquid to the top of the column, and the other liquefied portion is extracted as an ethylene oxide product through a conduit (57).

The uncondensed vapor in the condenser (52) of the ethylene oxide rectification column (50) passes through a conduit (55) to a re-ethylene oxide absorption column (not shown) to recover ethylene oxide.
supplied to

The bottom liquid of the ethylene oxide rectification column (50) is drawn out through a conduit (67) as necessary to separate heavy fractions of high-boiling point impurities such as acetaldehyde and acetic acid.

(Function) The function of the present invention is to introduce a reaction product gas containing ethylene oxide, which is produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst, into an ethylene oxide absorption tower and exchange it with an absorption liquid. A part of the gas from the top of the ethylene oxide absorption tower is circulated to the ethylene oxidation reaction process, and the bottom liquid of the ethylene oxide absorption tower containing ethylene oxide is supplied to the ethylene oxide stripping tower, and ethylene oxide is diffused from the top of the ethylene oxide stripping tower. The liquid extracted from the bottom of the ethylene oxide stripping tower exchanges heat with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then is cooled in a cooler and guided to the ethylene oxide absorption tower.
In the process where the absorption liquid is recycled and used, and the remainder is sent to the by-product ethylene glycol concentration tower to concentrate the ethylene glycol contained in the absorption liquid, the thermal energy of the steam dissipated from the top of the ethylene oxide stripping tower is used to heat the ethylene oxide rectification tower. The liquid extracted from the bottom of the ethylene oxide diffusion tower is used to exchange heat with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then a heat pump is used to recover the thermal energy of the absorption liquid to generate water vapor and produce ethylene oxide. This is a method for purifying ethylene oxide, which is used as a heating source for a rectification column and can be used as an absorption liquid for an ethylene oxide absorption column after the absorption liquid is cooled by a heat pump and is further cooled in a cooler.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the scope of the present invention is not limited only by this example.

Example 1 In Figure 1, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through a conduit (1) into a packed column or tray column. The ethylene oxide absorption tower (2) is supplied to the lower part of the ethylene oxide absorption tower (2) through the conduit (3) at a temperature of 40° C. or less, a pH of 6 or more, an ethylene glycol concentration of 1 to 20 wt. An absorbing liquid consisting of a foaming agent (water-soluble silicone emulsion) with a concentration of 1 to 5 oppm and the remainder being water was introduced and brought into countercurrent contact with the reaction product gas, so that ethylene oxide in the reaction product gas was absorbed into the absorbent. At this point, more than 99% by weight of ethylene oxide in the reaction product gas was recovered. Ethylene and oxygen that were not absorbed from the top of the ethylene oxide absorption tower (2)
Gases of impurity groups such as carbon dioxide, inert gases (nitrogen, argon, methane, ethane), aldehydes, acidic substances, etc. were circulated through conduit (3) to the carbon dioxide absorption step and/or the oxidation reaction step.

In this absorption process, in addition to ethylene oxide, low-point impurities such as ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane, etc.), formaldehyde generated in the ethylene oxidation reaction process, and high-temperature impurities such as acetaldehyde and acetic acid are added. A substantial amount of boiling point impurities were also absorbed at the same time.

The bottom liquid of the ethylene oxide absorption tower (2) is sent to the heat exchanger (6) through the conduit (5) to exchange heat with the ethylene oxide dispersion tower bottom liquid to raise the temperature to 70 to 110°C, and then to the conduit (7).
is sent to the gas-liquid separation tank (8), and the light component of the inert gas containing some ethylene oxide and water is sent to the conduit (9).
). After flushing the light gas, the remaining absorption liquid is passed through the conduit (10) at a pressure of 0.1 to 2 KO/c.
ta G S4 degrees Ethylene oxide is supplied to the upper part of the ethylene oxide stripping tower (11) at 85 to 120 °C, and the heating steam is supplied through the conduit (13) to the heater (12) of the ethylene oxide stripping tower (11). The bottom of the ethylene oxide stripping tower (11) was heated to a temperature of 100 to 13, substantially free of ethylene oxide.
A portion of the ethylene oxide stripping tower bottom liquid at 0°C is transferred to the conduit (14
) and the conduit (15) to the heat exchanger (6) for heat exchange with the bottom liquid of the ethylene oxide absorption tower. The absorption liquid leaving the heat exchanger (6) passes through the refrigerant evaporator (16), and then passes through the conduit (18) and conduit (19) into the condenser (
17) and then fresh water was introduced into the ethylene oxide absorption column (2) through conduit (21) to adjust the ethylene glycol concentration in the absorption liquid.

On the other hand, the remaining absorption liquid extracted from the bottom of the ethylene oxide stripping tower (11) through the conduit (14) is transferred to the conduit (22).
) was sent to the by-product ethylene glycol concentration column.

The refrigerant is evaporated by exchanging heat with the bottom liquid of the ethylene oxide stripping tower in the refrigerant evaporator (16), and then sent to the refrigerant compressor (70) through the conduit (71) and compressed, and then passed through the conduit (72) to the refrigerant condenser ( 73) to give heat to the external fluid and cause it to condense. The condensed refrigerant is re-allocated through the conduit (74).
The refrigerant was sent to the evaporator (16).

By circulating the water supplied from the conduit (78) to the refrigerant condenser (73), the conduit (76), the conduit (77), and the tank (75), water vapor is recovered through the conduit (59), and the water vapor is collected in the ethylene oxide rectification column. (50) was sent to the heater (60) as a heating source.

Table 1 shows the continuous operating conditions for this process.

On the other hand, the vapor containing ethylene oxide released from the top of the ethylene oxide stripping tower (11) is transferred to the conduit (23).
) to the heater (60) of the ethylene oxide rectification column (50) as a heating source, and then the condensed liquid and uncondensed vapor pass through the conduit (61) to the conduit (62) and the conduit (63).
), the condensed liquid is refluxed to the top of the ethylene oxide stripping tower (11) through the conduit (65), and the uncondensed vapor is sent to the dehydration tower (29) through the conduit (66). Supplied.

Heating the dehydration tower (29)! (30) by heating with a heating medium such as steam or Dow Sam (a product of Dow Company) through the conduit (31), or by a heating method that directly introduces steam into the lower part of the dehydration tower (29). )
Ethylene oxide-free water is withdrawn from the bottom of the column through a conduit (32).

Steam containing ethylene oxide is passed from the top of the dehydration tower (29) through the conduit (33) to the conduit (35) and the conduit (
A portion of the condensed liquid is returned to the top of the dehydration tower (29) through the conduit (37), and uncondensed vapor in the condenser (34) is sent to the condenser (34) through which cooling water passes through the conduit (36). 39) to a re-ethylene oxide absorption tower (not shown).

The slack part of the condensate is passed through the conduit (38) to the light fraction separation column (4).
0). Ethylene oxide vapor containing light fraction gas is transferred from the top of the light fraction separation column (40) to a conduit (43).
The condensate is sent to the condenser (44) through the conduit (47).
The uncondensed vapor was fed through conduit (48) to a re-ethylene oxide absorption column (not shown) for recovery of ethylene oxide. The bottom liquid of the light fraction separation column (40) is passed through the conduit (49
) to the ethylene oxide rectification column (50). The emitted material from the top of the ethylene oxide stripping tower (11) is supplied to the heater (60) of the ethylene oxide rectification tower (50), and the emitted material from the ethylene oxide absorption liquid is supplied to the heater (58) of the ethylene oxide rectification tower (50). Heat is recovered using a heat pump and water vapor generated from a tank (75) is heated through a conduit (59),
Bottom temperature of ethylene oxide rectification column (50) 35-80
°C, ethylene oxide rectification column bottom pressure 1, 1-8.1 kg
/cjG, and from the top of the ethylene oxide rectification column, the top temperature is 35 to 75°C, and the top pressure is 1 to 8 kQ/ca.
! Passing the ethylene oxide vapor of G through the conduit (51),
The ethylene oxide is sent to an ethylene oxide condenser (52) to liquefy the ethylene oxide, and a portion is supplied as a reflux liquid to the top of the ethylene oxide rectification column (50) through a conduit (56).
The other part was extracted as an ethylene oxide product through a conduit (57).

Uncondensed vapor from the ethylene oxide condenser (52) is transferred to the conduit (
55) was fed to a re-ethylene oxide absorption tower (not shown) for recovery of ethylene oxide.

The bottom liquid of the ethylene oxide rectification column (50) was extracted through a conduit (67) as necessary to separate heavy fractions of high-boiling point impurities such as acetaldehyde and acetic acid.

Table 1 shows the continuous operating conditions for this process.

Comparison Example 1 In Figure 2, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with molecular oxygen-containing gas in the presence of a silver catalyst is passed through conduit (1) into a packed column or tray column type. The absorption liquid is supplied to the lower part of the ethylene oxide absorption tower (2), and introduced into the upper part of the ethylene oxide absorption tower (2) through the conduit (3), and brought into countercurrent contact with the reaction product gas, so that the amount of the absorption liquid is 99% by weight or more in the reaction product gas. The gases such as ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane), aldehydes, and acidic substances that were not absorbed from the top of the ethylene oxide absorption tower (2) are collected through the conduit ( 4) to the carbon dioxide absorption step and/or oxidation reaction step. In this absorption process, in addition to ethylene oxide, ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane, etc.), low-boiling point impurities such as formaldehyde generated in the ethylene oxidation reaction process, and high-boiling point impurities such as acetaldehyde and acetic acid are used. A substantial amount of impurities are also absorbed at the same time. The bottom liquid of the ethylene oxide absorption tower (2) is transferred to the conduit (5
) to the heat exchanger (6) and exchange heat with the bottom liquid for ethylene oxide dispersion to raise the temperature to 70-110°C.
7) was sent to the gas-liquid separation tank (8), and the heavy portion of the inert gas containing a portion of ethylene oxide was separated through the conduit (9). The remaining absorption liquid after flushing the heavy gas is passed through the conduit (10) at a tower top pressure of 0.1 to 2 KQ.
/ ai G, is supplied to the upper part of the ethylene oxide stripping tower (11) at a temperature of 85 to 120°C, and heated by steam from the heater (12) of the ethylene oxide stripping tower (11), and the 99 weight of ethylene oxide contained in the absorption liquid is %
More than that! ! @Seshime, ethylene oxide stripping tower (11
) at a temperature substantially free of ethylene oxide [
A portion of the ethylene oxide stripping bottom liquid at 100 to 130°C passes through the conduit (14) and the conduit (15) to the heat exchanger (
6), the liquid is exchanged with the bottom liquid of the ethylene oxide absorption tower (2), cooled by a condenser (17) through which cooling water passes through the conduit (16), and then through the conduit (18) and the conduit (one conduit). Fresh water was introduced through conduit (21) to adjust the ethylene glycol concentration in the absorption liquid. During the oxidation process in which ethylene is oxidized with molecular oxygen and the ethylene oxide diffusion process, low boiling point impurities such as by-product ethylene glycol and formaldehyde, which are produced by the hydrolysis reaction of ethylene oxide and water in the absorption liquid, and high boiling point impurities such as acetaldehyde and acetic acid. In order to prevent an increase in impurities, the bottom liquid of the ethylene oxide stripping tower (11) was extracted from the bottom of the ethylene oxide stripping tower (11) through conduits (14) and (22) and sent to a by-product ethylene glycol concentration step.

On the other hand, the vapor containing ethylene oxide released from the top of the ethylene oxide stripping tower (11) is transferred to the conduit (23).
) to the condenser (24) through which cold water passes through the conduit (25) and conduit (26), and the condensate is transported to the top of the ethylene oxide stripping tower (11) through the conduit (27), where uncondensed vapor is is passed through the conduit (28) to the dehydration tower (29
).

A heating method in which the heater (30) of the dehydration tower (29) heats the water vapor or a heating medium such as Dow Sam (product of Dow Company) through the conduit (31), or directly introduces steam into the lower part of the dehydration tower (29). Heated with dehydration tower (29)
Ethylene oxide-free water was extracted from the bottom of the column through a conduit (32).

Steam containing ethylene oxide is passed from the top of the dehydration tower (29) through the conduit (33) to the conduit (35) and the conduit (
A portion of the condensed liquid is returned to the top of the dehydration tower (29) through the conduit (37), and uncondensed vapor in the condenser (34) is sent to the condenser (34) through which cooling water passes through the conduit (36). 39) to a re-ethylene oxide absorption tower (not shown).

The other part of the condensate from the condenser (34) was fed to the heavy fraction separation column (40) through a conduit (38).

Steam is heated by the heater (41) of the heavy fraction separation column (40) through a conduit (42), and ethylene oxide vapor containing heavy fraction is released from the top of the heavy fraction separation column (40). The condensed liquid is sent to the condenser (44) through the conduit (43), and a part of the condensate is sent to the heavy fraction separation column (47) through the conduit (47).
40) and the uncondensed vapors were fed through conduit (48) to a re-ethylene oxide absorption column (not shown) for recovery of ethylene oxide.

It was supplied from the bottom of the heavy fraction separation column (40) to the ethylene oxide rectification column (50) through a conduit (49).

The water vapor is heated by the heater (58) of the ethylene oxide rectification column (50) by heating it through the conduits (5).
) from the conduit (59) to pressure 0, 5 to 1, 0 k Q
/cjG steam is supplied to the ethylene oxide rectification column (
50), the bottom temperature of the ethylene oxide rectification column was 62°C and the bottom pressure of the ethylene oxide rectification column was 3.7 ko/cri G.
The ethylene oxide vapor of QlcdG is sent to the condenser (52) through the conduit (51), and the ethylene oxide vapor is liquefied, and a part of the liquefied product is introduced as a reflux liquid to the top of the ethylene oxide rectification column (50) through the conduit (56). ,
The other liquefied portion was extracted as an ethylene oxide product through a conduit (57).

The uncondensed vapor in the condenser (52) of the ethylene oxide rectification column (50) passes through a conduit (55) to a re-ethylene oxide absorption column (not shown) to recover ethylene oxide.
was supplied to.

The bottom liquid of the ethylene oxide rectification column (50) was drawn out through a conduit (67) as necessary to separate heavy fractions of high-boiling point impurities such as acetaldehyde and vinegar M.

Table 2 summarizes the continuous operating conditions for this process.

(Effects of the Invention) According to the method of the present invention, the thermal energy of the steam dissipated from the top of the ethylene oxide stripping column is introduced into the ethylene oxide rectification column reboiler, and the liquid extracted from the bottom of the ethylene oxide stripping column is heat-exchanged. After exchanging heat with the bottom liquid of the ethylene oxide absorption tower using a heat pump, the thermal energy of the absorption liquid is recovered using a heat pump to generate steam, which is introduced into the ethylene oxide rectification tower reboiler to heat the ethylene oxide rectification tower. This exhibits the effect of making it possible to significantly reduce the amount of external heating heat trapped. Furthermore, implementing this method has the effect of reducing the thermal load of the cooling water that cools the vapor phase generated at the top of the ethylene oxide rectification column.

[Brief explanation of drawings]

FIG. 1 is an example showing a preferred specific example of the ethylene oxide purification method of the present invention. FIG. 2 is an example showing a known ethylene oxide purification method related to the present invention. (2) Ethylene oxide absorption tower (6) Heat exchanger (8) Gas-liquid separation tank (11) Ethylene oxide stripping tower (12) Ethylene oxide stripping tower heater (16) Refrigerant evaporator (17) Cooler (24) Ethylene oxide stripping tower Condenser (29) Dehydration tower (30) Dehydration tower heater (34) Dehydration tower condenser (40) Heavy fraction separation tower (41) Heavy fraction separation tower heater (44) Heavy fraction separation tower condenser ( 50) Ethylene oxide rectification column (52) Ethylene oxide rectification column condenser (58) Ethylene oxide rectification column heater (60) Ethylene oxide rectification column heater (64) Ethylene oxide stripping column condenser (70) Refrigerant compressor (73) Refrigerant condenser (75) Flash tank

Claims (1)

[Claims] (1) A reaction product gas containing ethylene oxide produced by contact vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower, brought into countercurrent contact with the absorption liquid, and the ethylene oxide absorption tower A part of the gas from the top is circulated to the ethylene oxidation reaction process, and the ethylene oxide absorption column bottom liquid containing ethylene oxide is supplied to the ethylene oxide stripping column, where ethylene oxide is dissipated from the top of the ethylene oxide stripping column, and a distillate containing ethylene oxide and water is produced. It is condensed and the water is separated in a dehydration tower.
In the process of separating light fractions in a light fraction separation column and then rectifying ethylene oxide in an ethylene oxide rectification column,
The emitted material emitted from the ethylene oxide stripping tower is used as a heating source for the ethylene oxide rectification tower, and the liquid extracted from the bottom of the ethylene oxide stripping tower is guided to the ethylene oxide absorption tower and recycled as an absorption liquid.The remainder is used as the ethylene contained in the absorption liquid. In order to concentrate the glycol, the by-product ethylene glycol is sent to the concentration tower, and the liquid extracted from the bottom of the ethylene oxide diffusion tower is heat exchanged with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then the thermal energy of the absorption liquid is transferred using a heat pump. Purification of ethylene oxide, characterized in that the collected water vapor is generated and used as a heating source for an ethylene oxide rectification tower, and the absorption liquid cooled by a heat pump is further cooled in a cooler and then used as the absorption liquid for the ethylene oxide absorption tower. Method.